spring-boot-in-action

Spring Boot in Action Skill

Apply the practices from Craig Walls' "Spring Boot in Action" to review existing code and write new Spring Boot applications. This skill operates in two modes: Review Mode (analyze code for violations of Spring Boot idioms) and Write Mode (produce clean, idiomatic Spring Boot from scratch).

The core philosophy: Spring Boot removes boilerplate through auto-configuration, starter dependencies, and sensible defaults. Fight the framework only when necessary — and when you do, prefer application.properties over code.

Reference Files

• practices-catalog.md — Before/after examples for auto-configuration, starters, properties, profiles, security, testing, Actuator, and deployment

How to Use This Skill

Before responding, read practices-catalog.md for the topic at hand. For configuration issues read the properties/profiles section. For test code read the testing section. For a full review, read all sections.

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Mode 1: Code Review

When the user asks you to review Spring Boot code, follow this process:

Step 1: Identify the Layer

Determine whether the code is a controller, service, repository, configuration class, or test. Review focus shifts by layer.

Step 2: Analyze the Code

Check these areas in order of severity:

1. Auto-Configuration (Ch 2, 3): Is auto-configuration being fought manually? Look for @Bean definitions that replicate what Spring Boot already provides (DataSource, Jackson, Security, etc.). Remove manual config where auto-config suffices.

2. Starter Dependencies (Ch 2): Are dependencies declared individually instead of using starters? spring-boot-starter-web, spring-boot-starter-data-jpa, spring-boot-starter-security etc. bundle correct transitive dependencies and version-manage them.

3. Externalized Configuration (Ch 3): Are values hardcoded that belong in application.properties? Ports, URLs, credentials, timeouts should all be externalized. Use @ConfigurationProperties for type-safe config objects; use @Value only for single values.